Move haproxy httpchk configuration per-listen as zope's webdav returns 401
on (at least) GET / . TCP-level checks are still active, which should be
sufficient.
Also, change zope_family_address_list check to getitem as it's more natural
than concatenating.
Also, stop using apache.zope.backend recipe to add support for per-port
scheme so automatic ERP5Site creation knows which URL is really HTTP.
Also, stop using certificate_authority recipe and call openssl directly
when generating self-signed cert for https/webdavs support.
Also, rework balancer parameters a bit (still undocumented).
Also, make instance-balancer always publish ipv6 value (empty when no ipv6
available), so instance-erp5 always succeeds.

Dot not move longrequest-logger parameters out yet, as they belong to
another section.

Check got removed from code, comment lingers on.

Escaping is right, but "raw" context entry type does not de-serialise, so
deadlock debugger password was stored in an unintended format. Moving
deadlock_debugger_password to a buildout section involves required magic.
Move other parameters for consistency.
Also, honour deadlock_path parameter, which was previously ignored.

Do not expose a parameter, as index can be reconstructed from data anyway.
Rotating is anyway needed as index backup can take a significant amount of
space for rare practical use.
Also, remove this point from TODO.

I reviewed parameters (both in code and in documentation) and think they are
now consistent and sane enough to not block a merge.

Balancer parameters were and are not supported, so this compatibility
breakage is not important.
The goal of this change is to make balancer parameter layout consistent
with other software-types.
Also, balancer's base TCP port is not taken from empty-string parameter
anymore.

inkscape seems not to start with glib 2.39 or later like :
futex(0x7fff41df100c, FUTEX_WAIT_BITSET_PRIVATE|FUTEX_CLOCK_REALTIME, 1, NULL, 7ffedf9a4a00) = -1 EAGAIN (Resource temporarily unavailable)

They contain section references, not immediate values, so they are intended
to be evaluated by buildout and hence must not be escaped.